Right upper lobe atelectasis is easily detected as the lobe migrates
superomedially toward the apex and mediastinum. The minor fissure elevates
and the inferior border of the collapsed lobe is a well demarcated curvilinear
border arcing from the hilum towards the apex with inferior concavity.
Due to reactive hyperaeration of the lower lobe, the lower lobe artery
will often be displaced superiorly on a frontal view.

The arrows point to the horizantal fissure. Notice the normal position
of the pulmonary arteries in this patient.